function validateForm() {
	var checked = 0;
	var total = document.FormName.elements.length;
	for(i = 0; i < total; i++)
	{
		if(document.FormName.elements[i].type == "checkbox") {
			if(document.FormName.elements[i].checked)
				checked++;
		}
	}
	
	// adjust this for more checkboxes
	if(checked > 1)
		return false;
	
	return true;
}

